BACKGROUND: In Spain, two smoke-free laws have been passed (Law 28/2005 and Law 42/2010).This study evaluates the association between Spanish smoking legislations and the second-hand smoke (SHS) exposure in an adult non-smoking population cohort in Barcelona (Spain). METHODS: This is a longitudinal study, before and after the implementation of two national smoking bans, in a representative sample of adults (≥16years old) from Barcelona (Spain) surveyed in 2004-2005 and followed up in 2013-2014 (n=736). We only analyzed non-smokers (n=397). We obtained 9ml of saliva sample for analysis of cotinine, a biomarker of recent tobacco exposure. We calculated geometric means of salivary cotinine concentration and their geometric standard deviation. We used linear mixed effect models, with individuals as random effects, to model the percentage change in salivary cotinine concentration and their 95% confidence intervals. RESULTS: The percentage of participants with saliva samples with measurable concentrations of cotinine fell from 92.4% to 64.2% after both Spanish smoking legislations. The geometric mean of salivary cotinine concentration significantly decreased 88% (from 0.98ng/mL to 0.12ng/mL, p<0.001) after the implementation of the two Spanish smoke-free legislations. The decrease of the GM salivary cotinine concentration was statistically significant independently of the sociodemographic variables. CONCLUSION: There was a large reduction in the salivary cotinine concentration among adult non-smokers and higher cotinine concentrations among those declaring exposure to SHS at home after both legislations. Moreover, after both Spanish smoke-free laws salivary cotinine concentration was homogenized according to sociodemographic variables

This project was co-funded by the Instituto de Salud Carlos III, Subdirección General de Evaluación, Government of Spain (RTICC RD12/0036/0053, PI12/01114 and PI12/01119), and the Ministry of Universities and Research, Government of Catalonia (grant 2014SGR999 and 2014SGR00680) from the Government of Catalonia, and co-funded by ISCIII-Subdirección General de Evaluación and by FEDER funds/European Regional Development Fund (ERDF) −a way to build Europe-. This work was also partially funded by the European Union’s Horizon 2020 Research and Innovation Programme (The TackSHS Project; grant agreement: 681040).